Cup of "Joe"

I got into a little "discussion" a few days ago about how coffee came to be known as "a cup of Joe". As none of you may know I am in the US Navy (and if you do know, STOP STALKING ME!) and many of my colleagues believe the phrase stems from Admiral Josephus Daniels' (Secretary of the Navy 1912-1920) banning of alcohol onboard US Navy ships (thanks a lot Joe). Its even become the official backstory on the Navy's own Origins of Naval Terminology website.

Unfortunately the dates don't pan out. US Navy Ships had been dry since 1862, it wasn't until 1893 that the wardrooms were allowed wine messes (bloody officers). General Order 99

"The use or introduction for drinking purposes of alcoholic liquors onboard any naval vessel or within any navy yard or station, is strictly prohibited, and commanding officers will be held directly responsible for the enforcement of this order."

wasn't issued until 1914 - except for the wardroom itself (comprising a small fraction of the total complement) ships had been dry for a bit over 50 years. Even the wardrooms were limited to wine and similar. Add into this, that the earliest written record of the phrase "cup of Joe" doesn't appear until 1930 - 16 years after ships were completely dry and 10 years after the man who gave that order was gone.

Because the phrase first shows up in 1930 its wouldn't be derived from "GI Joe" (apparently a slang term for soldiers and not a cartoon) which doesn't appear until the WWII timeframe.

The most likely explanation (and backed up by an entry in the Reserve Officer's manual of 1931) is that the phrase comes from a corruption of the other terms for coffee like Java or Mocha.